A bypass type turbofan jet engine typically includes a nacelle or cowling surrounding a jet engine core and defining a flow-through duct for prop driven airflow. The airflow through this duct follows the contour of the engine from front to rear, providing forward thrust for the aircraft. When reverse thrust is required to slow the aircraft during landing or while cruising, a thrust reverser is deployed at the rear of the cowling, deflecting the airflow through a ring of turning vanes, which are exposed as an aft section of the cowling is moved toward the rear of the engine. The turning vanes redirect the airflow radially outward and back toward the front of the engine, producing the required reverse thrust.
In an ultrahigh bypass engine, the engine core has a relatively large diameter and the nacelle surrounding the engine must have a much larger diameter than the nacelle used in a conventional bypass engine. In addition, compared to the nacelles on conventional bypass turbofan engines, the nacelles used on ultrahigh bypass engines have a more conical shape, converging radially inward at their trailing edge to a greater extent. Their shape makes it difficult to adapt the prior art thrust reversers for use with such engines without increasing the thickness of the portion of the cowling in which the turning vanes are recessed. Becaue it is housed in the aft portion of the cowling, the turning vane ring used in prior art designs would have to have substantially the same convergent shape as the nacelle aft end. Additional cross-sectional thickness in the cowling would be needed so that the rear portion of the nacelle could clear the converging aft end of the turning vane ring during its deployment. A thrust reverser of the prior art design would thus be excessively heavy if scaled-up for use on an ultrahigh bypass engine, would require a longer fan cowl, and would add significant drag to the engine due to an increase in the cross-sectional area of the cowling.
Accordingly, the present invention provides a thrust reverser that has a relatively thin cross section, with minimal drag. Furthermore, this thrust reverser adds less weight to the nacelle of an ultrahigh bypass engine than would a thrust reverser of conventional design. These and other advantages of the present invention will be apparent from the attached drawings and the description of the preferred embodiments that follows below.